Local expression of lipopolysaccharide-binding protein in human gingival tissues

Background: Lipopolysaccharide-binding protein (LBP) functions as a crucial molecule in innate host defense responses to bacterial challenge through neutralization of bacterial lipopolysaccharide (LPS) and activation of cellular responses. Objectives: This study was to investigate the expression profile and levels of LBP in gingival tissues and their associations with periodontal health and disease. Methods: Gingival biopsies were collected from 44 chronic periodontitis patients, including periodontal pocket tissues (PoTs) and the adjacent healthy gingival tissues (HT-Ps), as well as from 15 periodontally healthy subjects as controls (HT-Cs). The peptide and mRNA of LBP were detected by semi-quantitative immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR), respectively. Results: LBP peptide was detected in 90.9% of PoTs (20/22), 84.6% of HT-Ps (11/13) and all HT-Cs (7/7). The expression of LBP was mainly confined to the cytoplasm of granular and keratinized layers of gingival epithelium, spreading from the oral sulcular epithelium to oral epithelium with the expression density decreasing gradually from coronal to apical portion. LBP peptide was also found on endothelial surfaces and/or inside the lumens of blood vessels in connective tissues. The mean LBP expression levels in HT-Cs were significantly higher than those in HT-Ps and PoTs. LBP mRNA was detected in 55% of PoTs (11/20), 55% of HT-Ps (11/20) and 75% of HT-Cs (6/8). Conclusions: We for the first time found the expression of LBP peptide and mRNA in human gingival tissues. Local expression of LBP in gingival tissues might contribute to periodontal homeostasis.